FIGURE 3:

Acute ER stress does not inhibit insulin-stimulated phosphorylation of IRS1 at four specific tyrosine phosphorylation sites in C₂C₁₂ myotubes. Tyrosine phosphorylation at (A) Y608, (B) Y628, (C) Y891, and (D) Y935 was analyzed by Western blotting. C₂C₁₂ myotubes were serum-starved for 18 h before exposure to 1 μM thapsigargin for 10, 20, or 30 min (left side of figure panels) or to 0.1, 1.0, or 10 μg/ml tunicamycin for 30 min (right side of figure panels), followed by stimulation with the indicated concentrations of insulin for 5 min in the continued presence of thapsigargin or tunicamycin. Bars represent SEs (n = 3). p values for comparison of effects of thapsigargin or tunicamycin within one insulin concentration and for comparison of effects of different insulin concentrations were calculated by ordinary two-way ANOVA with Tukey’s multiple comparisons test (Tukey, 1949a). Abbreviation: α-Tub, α-tubulin.